1. Field of the Invention
The present invention relates to a method of making a T-shaped write head with less side writing and, more particularly, to a T-shaped write head wherein an uppermost pole tip component at the ABS has slanted surface portions which minimize flux leakage between the uppermost pole tip component and a bottommost pole tip component.
2. Description of the Related Art
The heart of a computer is a magnetic disk drive which includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The suspension arm urges the slider into contact with the surface of the disk when the disk is not rotating but, when the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic field signals from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
A write head typically employs ferromagnetic first and second pole pieces which are capable of carrying flux signals for the purpose of writing the magnetic impressions into the track. Each of the first and second pole pieces has a pole tip, a yoke and a back gap with the yoke being located between the pole tip and the back gap. The pole tips are located at the ABS and the back gaps are magnetically connected at a recessed location within the write head. At least one coil layer is embedded in an insulation stack between the yokes of the first and second pole pieces. A nonmagnetic write gap layer is located between the pole tips. Processing circuitry digitally energizes the write coil which induces flux signals into the first and second pole pieces. The flux signals bridge across the write gap at the ABS so as to write the aforementioned magnetic impressions or bits into the track of the rotating disk. The thinner the thickness of the write gap layer, the greater the number of bits the write head can write into the track.
A write head is typically rated by its areal density which is a product of its linear bit density and its track width density. The linear bit density is the number of bits which can be written per linear inch along the track of the rotating magnetic disk and the track width density is the number of tracks that can be written per inch along a radius of the rotating magnetic disk. The linear bit density is quantified as bits per inch (BPI) and the track width density is quantified as tracks per inch (TPI). As discussed hereinabove, the linear bit density depends upon the thickness of the write gap layer. The track width density is directly dependent upon the width of the second pole tip at the ABS. Efforts over the years to increase the areal density of write heads have resulted in computer storage capacities increasing from kilobytes to megabytes to gigabytes.
The first and second pole pieces are typically fabricated by frame plating. Photoresist is employed to provide the frame and a seed layer is employed to provide a return path for the plating operation. A typical sequence for fabricating a pole piece is to sputter clean the wafer, sputter deposit a seed layer, such as nickel iron, on the wafer, spin a layer of photoresist on the wafer, light-image the photoresist layer through a mask to expose areas of the photoresist that are to be removed (assuming that the photoresist is a positive photoresist), develop the photoresist to remove the light-exposed areas to provide an opening in the photoresist and then plate the pole piece in the opening up to a desired height.
The magnetic moment of each pole piece is parallel to the ABS and to the major planes of the layers of the write head. When the write current is applied to the coil of the write head the magnetic moment rotates toward or away from the ABS, depending upon whether the write signal is positive or negative. When the magnetic moment is rotated from the parallel position, the aforementioned magnetic flux fringes across the write gap layer between the first and second pole pieces impressing a positive or negative bit in the track of the rotating magnetic disk. As the write current frequency is increased, the linear bit density is also increased. An increase in the linear bit density is desirable in order to increase the aforementioned areal density which provides a computer with increased storage capacity.
One type of write head is referred to as a T-shaped write head. A T-shaped write head typically has three layers of soft magnetic material exposed at the ABS to the disk which are referred to as P1, P2 and P3. P1 refers to the lower pole while P2 and P3 are joined together and comprise the upper pole. By design, the lateral dimension of the P2 layer defines the width of the magnetic bits on the disk. One problem with these heads is that the lateral dimension of P3 is typically wider than P2. Therefore, the outer regions of P3 can disturb the magnetic material in bits other than the one being written, which is referred to as a bit definition problem. This occurs because the head produces a field in locations other than the location desired, because of the extra magnetic material in the P3 layer which is outside the width of the P2 layer.
The upper pole is typically fabricated in several stages, namely: P2 plating, P2 insulator fill deposition, P2 planarization and P3 plating. Each of these steps consists of several smaller steps, such as depositions, etchings and photolithography patterning steps.
The P2 planarization step is very important since it determines the structure of the interface between P2 and P3. This step is usually performed in such a way that the P2 layer and the P2 insulator fill layer are planarized with their top surfaces coplanar. The P3 layer is then formed onto a nearly flat surface. Because of process variations the P3 width must be made wider than the P2 width, which means that P3 always contains extra magnetic material outside the width of P2. This extra magnetic material is a problem partly because a right angle is formed at the lower corners of P3. It is widely known that magnetic material which is shaped into sharp corners has a tendency to produce large magnetic fields.